The overall objective is to provide demographers, statisticians and population researchers with the means for assessing the likely levels of bias in demographic indices derived from census and/or sample survey data. The ultimate goal is to produce two sets of tables, the first of which will show the level of net error in such indices as crude birth and death rates, age-specific fertility rates, total fertility, infant mortality and age-specific death rates over a range of reporting errors concerning ages and the occurrence of vital events for selected combinations of (1) population structures, (2) fertility and mortality patterns and (3) trends. The second set of tables will show the level of net error in demographic indices derived by using analytic techniques which have been developed specifically to make adjustments for reporting errors. In essence the latter tables will estimate the robustness of these analytic techniques when the assumptions upon which they are based are not satisfied. A two step simulation process will be used to compute the levels of net error or bias. In the first step the vital event history for each individual in a sample representing a particular model population will be simulated using the dynamic computerized demographic microsimulation model POPSIM. In the second step, the collection of demographic data from the same population, with and without reporting errors, will be simulated. Demographic indices will then be computed for both the contaminated and error-free simulated data and compared. This process will be repeated for a range of populations and levels of gross reporting errors. A similar procedure will be used to estimate the robustness of techniques designed to adjust for errors in demographic data.